Trichanthecium Zuloaga & Morrone (2011: 13)

Zuloaga, Fernando Omar, Aliscioni, Sandra, Delfini, Carolina & Salariato, Diego Leonel, 2024, Old World species of Trichanthecium (Poaceae: Panicoideae: Paniceae) including a new species from the Democratic Republic of Congo, Phytotaxa 646 (3), pp. 230-264 : 236-238

Trichanthecium Zuloaga & Morrone (2011: 13) .

Type:— Trichanthecium parvifolium (Lam.) Zuloaga & Morrone

(≡ Panicum parvifolium Lam. )

Annuals or perennials, with culms decumbent and rooting at the lower nodes, to erect and cespitose; internodes hollow. Ligules membranous, shortly laciniate at the apex. Blades filiform to ovate-lanceolate, flat or inrolled. Inflorescence an open panicle, with first-order branches alternate and divergent; spikelets solitary on long pedicels. Spikelets dorsally compressed, 2-flowered, disarticulating below the glumes; lower glume (1/4–)1/2 or as long as the spikelet, nerveless to (1–)3-nerved, with or without a long mucronate tip, stipe conspicuous or not between the lower and upper glume; upper glume 3–5(–7)-nerved; lower lemma subequal to the lower lemma, 5(–7)-nerved; lower palea reduced to as long as the lower lemma, hyaline; lower flower staminate or neuter; upper anthecium indurate, muticous, usually pale, covered with bicellular microhairs, occasionally glabrous, and simple papillae evenly distributed all over its surface or absent; occasionally with long macrohairs, smooth; upper lemma 5-nerved. Caryopsis with a punctiform to elliptic hilum; embryo less than 1/2 the length of the caryopsis. Chromosome number: x = 9.

A genus with 52 species, distributed in America, continental Africa, and Madagascar ( Zuloaga et al. 2011).

Key to the Old World species of Trichanthecium

* Species marked with an asterisk were treated before in Zuloaga et al. (2011) and Xanthos et al. (2020)

1. Rachilla prominent between the lower and upper glume ................................................................................................. T. mueense *

- Rachilla inconspicuous between the lower and upper glume.............................................................................................................2

2. Lower glume with two tuberculate hairs toward the apex ........................................................................................ T. marunguensis

- Lower glume glabrous or pilose, without two tuberculate hairs toward the apex..............................................................................3

3. Plants tufted, culms erect, not decumbent, branching and rooting at the lower nodes; perennials....................................................4

- Plants not tufted, with culms decumbent, branching and rooting at the lower nodes; annuals or perennials..................................13

4. Blades filiform, 1–2 mm wide............................................................................................................................................................5

- Blades linear to ovate-lanceolate, (2–) 3–11 mm wide .......................................................................................................................6

5. Blades 8–25 cm long; spikelets 2–2.4 mm long, glabrous............................................................................................. T. natalense *

- Blades 1–4 cm long; spikelets 1.3–1.5 mm long, sparsely papillose-pilose, occasionally glabrous............................... T. filifolium *

6. Upper anthecium glabrous..................................................................................................................................................................7

- Upper anthecium with bicellular microhairs on its surface................................................................................................................9

7 Spikelets with glumes and lower lemma glabrous .................................................................................................................. T. eickii

- Spikelets with glumes and lower lemma pilose .................................................................................................................................8

8. Blades lanceolate, 3–6 mm wide, flat, subcordate at the base; spikelets 2–2.7 mm long........................................... T. inaequilatum

- Blades linear, 2(–3) mm wide, involute, narrowed at the base; spikelets 3–3.5 mm long ......................................... T. striatissimum

9. Upper anthecium with elongated bicellular microhairs, the distal cell elongated................................................... T. brazzavillense *

- Upper anthecium with globose bicellular microhairs, the distal cell globose..................................................................................10

10. Spikelets 2.4–3 mm long ....................................................................................................................................... T. margaritiferum *

- Spikelets (1.5–)1.8–2.2(–2.4) mm long............................................................................................................................................11

11. Spikelets 1.5–1.7 mm long ....................................................................................................................................... T. strictissimum *

- Spikelets (1.7–)1.8–2.2(–2.4) mm long............................................................................................................................................12

12. Blades lanceolate, (3–) 5–10 mm wide; culms erect; spikelets usually glabrous .......................................................... T. praealtum *

- Blades linear-lanceolate, 2–5 mm wide; culms ascending to erect; spikelets usually pilose.......................................... T. nervatum *

13. Upper glume with whitish hairs 3–4 mm long toward the apex................................................................................... T. acrotrichum

- Upper glume glabrous, if pilose shortly hairy and without hairs 3–4 mm long at the apex ............................................................14

14. Lower glume 1/6 to 1/4 times the length of the spikelet, nerveless; upper glume aristate, awn up to 1 mm long ....... T. delicatulum

- Lower glume (1/4–)1/2 times to as long as the spikelet, (1–)3–5-nerved; upper glume acute to acuminate, not aristate ...............15

15. Blades cordate and amplexicaul at the base .....................................................................................................................................16

- Blades attenuate to subcordate, not amplexicaul, at the base...........................................................................................................18

16. Spikelets 1.6–1.9 mm long; lower flower staminate; upper anthecium with globose bicellular microhairs .................. T. dinklagei *

- Spikelets 2–2.5 mm long; lower flower staminate or neuter; upper anthecium glabrous ................................................................17

17. Lower glume 1/2 to 2/3 times the length of the spikelet, 1–3-nerved, acute; lower palea absent........................................ T. calvum

- Lower glume 1/4 to 1/3 times the length of the spikelet, nerveless to 1-nerved, obtuse to acute; lower palea present........ T. wiehei

18. Lower palea reduced; lower flower neuter.......................................................................................................................................19

- Lower palea almost as long as the lower lemma; lower flower staminate.......................................................................................20

19. Spikelets 2.5–2.8(–3) mm long; blades linear; plants perennial; endemic to Madagascar................................................. T. perrieri

- Spikelets 1.5–2 mm long; blades ovate-lanceolate; plants annual; continental Africa ...................................................... T. pusillum

20. Upper anthecium with globose bicellular microhairs; spikelets 1–2.4 mm long .............................................................................21

- Upper anthecium glabrous; spikelets 2.2–3 mm long ......................................................................................................................25

21. Blades linear-lanceolate, narrowed at the base.................................................................................................................................22

- Blades ovate to ovate-lanceolate, subcordate at the base.................................................................................................................23

22. Spikelets 1–1.8 mm long, papillose-pilose with long tuberculate hairs........................................................................... T. tenellum *

- Spikelets 2–2.4 mm long, glabrous ............................................................................................................................ T. gracilicaule *

23. Spikelets with tuberculate hairs........................................................................................................................................ T. tenerium *

- Spikelets glabrous or pilose, but without tuberculate hairs..............................................................................................................24

24. Spikelets ellipsoid, the upper glume and lower lemma acuminate; upper anthecium 0.6–1 mm long, shorter than the spikelet........ ................................................................................................................................................................................. T. glaucocladum *

- Spikelets globose, the upper glume and lower lemma obtuse; upper anthecium 1.1–1.8 mm long, almost as long as the spikelet.... ..................................................................................................................................................................................... T. parvifolium *

25. Spikelets pilose.................................................................................................................................................................................26

- Spikelets glabrous.............................................................................................................................................................................27

26. Spikelets narrowly ovoid, 2.5–3 mm long; lower glume almost as long as the spikelet................................................ T. aequinerve

26’. Spikelets oblong in outline, 2.2–2.5(–2.6) mm long; lower glume 2/3 to 3/4 the length of the spikelet...................... T. hochstetteri

27. Spikelets narrowly ovoid, glabrous ............................................................................................................................... T. chionachne

- Spikelets oblong in outline, sparsely pubescent, rarely glabrous.................................................................................. T. hochstetteri